STORY ARCHIVE

Kakadu Dolphins

Few species of large mammals are yet to be described by scientists these days, especially cetaceans like whales or dolphins.

The newest species of dolphin, described only three years ago, happens to be native to Australia – the Snubfin Dolphin.

Long assumed to be the Irrawaddy Dolphin of SE Asia, the Australian Snubfin lives right across our tropical north, from Townsville to Broome. It coexists with another species, the Indo-Pacific Humpback Dolphin.

In the Northern Territory, scientists are researching their ecology for the first time. The giant river mouths of Kakadu National Park are particularly remote and hard to reach – the ideal place to search for dolphins.

“It’s probably one of the toughest kind of field trips you could do”, says zoologist Carol Palmer. “Depending on the time of year, the weather can be good or it can be abysmal.”

That’s exactly what Catalyst reporter Mark Horstman discovers in two searches for the elusive snubfin, at the end of the dry season and the beginning of the big wet.

TRANSCRIPT

Narration: There are few things more exciting than speeding on a fast boat at dawn towards an unknown scientific frontier.

The South Alligator River is the largest in Kakadu, one of the few rivers in the world with its entire catchment in a national park, from the headwaters to the sea.

Tidal for nearly a hundred kilometres inland, this marine environment is the least known part of our best known World Heritage area.

Hidden in these murky waters are much more than mangroves, mudbanks, and saltwater crocodiles.

I’ve joined these two national park boats on their monthly expedition to reveal the dolphins of Kakadu for the first time.

In the shallow coastal waters from Western Australia to Queensland are two sympatric species, that is, they live together.

We’re hoping to find them here: the Indo-Pacific Humpback Dolphin, and the Australian Snubfin Dolphin.

Most of what is known about these rare species comes from research in Queensland.

Carol Palmer: This is the first dolphin research or cetacean research to happen in the Northern Territory so it’s really important.

Narration: Zoologist Carol Palmer is working with the Kakadu rangers to protect these dolphins by discovering what they need to survive.

Carol Palmer: When we go to the humpback, what I always go on apart from the dorsal fin is that really long beak.

Fred Baird: Yes it is long, he comes out of the water a bit higher than the snubfin dolphin as well.

Carol Palmer: The snubfin has a really blunt head, I think he looks like a dugong, almost, except he’s got a dorsal fin.

Narration: So little is known about the snubfin that we’re not really sure how many there are. It wasn’t until 2005 that science discovered it to be a species in its own right, native to Australia. DNA analysis from Townsville described the first new dolphin species in more than fifty years.

Carol Palmer: At the moment it stands that certainly the Queensland populations are a separate species.

Narration: To find out if the Kakadu snubfins are the same, Carol needs to collect their DNA.

Carol Palmer: We use a modified twenty-two rifle, that’s a dart gun, has a cutting head on the end of the dart.

Narration: Her technique may look alarming, but it’s safer for the dolphins than trying to catch them.

Carol Palmer: The aim is to hit them with the dart just behind the dorsal fin … there’s a dolphin…and the little cutting head takes a piece of tissue, the dart floats and we retrieve the piece of tissue.

It’s been used worldwide on a whole range of different dolphin species and yeah we’re really looking forward to the opportunity to be able to use it.

Narration: But first we have to find them. I have a new-found respect for the difficulty of this research.

Carol Palmer: It’s probably one of the toughest kind of field trips you could do. The weather can just be abysmal.

Narration: And that’s what it proved to be the first time I travelled here four months ago – the coldest June day on record, the choppy sea hiding any dolphins.

Carol Palmer: This project is just new, and there could be some seasonality with their movement, they might have actually moved away. You’ve got to put in the time every month, come here, record what you see and what you don’t see, and over time you’ll actually pick up some of those patterns.

Narration: The next morning, I’m prepared to admit that maybe dolphin research is not as glamorous as it sounds.

Mark Horstman: This is the mouth of the South Alligator River, and its prime country for dolphins. We’ve been camping here on this boat, all night, in clouds of mosquitoes, an eight metre tide racing underneath us, so we’re here at first light to continue our search for the elusive snubfin dolphin.

Narration: This time, luck was against us. But a few weeks earlier off Broome in the Kimberley, another group of researchers had the perfect conditions.

They found exactly what we were looking for –snubfin dolphins feeding on squid and fish, in small pods of usually less than six.

Video like this is even harder to find than the dolphins.

It’s now late October, and the dry season is coming to an end. The Kakadu sky is starting to boil over.

Which brings me back to our search on the South Alligator River. This time we camp on a narrow strip of beach at the mouth, to start searching at sunrise on just the right tide.

Carol Palmer: Hopefully the snubbies and the humpback dolphins will be following this tide line, and there’s usually a tide line running down the middle of the river too.

Mark Horstman: If I thought it was a challenge last time, this time it’s nearly the wet season. Thirty-five degree heat every day, thunderstorm just about every afternoon, but there’s got to be a snubfin dolphin just around that corner.

Narration: So far, in six surveys of two days each month, Carol has seen 16 snubfins and 26 humpbacks.

Carol Palmer: Hopefully over time we’ll be able to get a bit of a picture of what’s the ideal habitat, but also just the range of habitats that the animals need over the year or over the years.

Mark: You’ve got these huge tides pumping in and out everyday, and then megatonnes of freshwater in the wet season, everything shifting around, whether its water or sandbanks...

Carol Palmer: And we’ve got dolphins at the front….

Mark Horstman: We’ve got dolphins!

Narration: At last, we’ve found some Indo-Pacific humpback dolphins.

Mark: There’s a second one.

Carol Palmer: Mum and calf. I wish it was a snubfin…but we know so little about the humpback dolphin and the snubfins, both of them should really have an equal footing in the research that we do.

Narration: The colours and marks on their fins are so distinctive that Carol uses them for identification.

Carol Palmer: We can search each fin through this catalogue and pick up the number of individuals, but also the number of times we’re seeing one particular individual.

Narration: It’s crucial for getting the first estimate of their population size here, especially when little is known about their reproductive biology.

Carol Palmer: All we’re going on is the great work that went on in Queensland, and it looks like they occur in small populations. The populations are isolated, they’re a long-lived slow-breeding animal and when you put all that into the mix you’d have to say that the animal is vulnerable.

Narration: Ironically, their greatest threat is death by drowning.

Carol Palmer: Looking at the threats worldwide to these coastal dolphins, really gill-netting is one of the biggest threats to them.

Narration: And now we know we have our own Australian species, under international law, we’re obliged to ensure its survival.

Carol Palmer: These rivers are very healthy with abundant fish life. So it’s a great place for a dolphin to be.